Semiconductor device and method for manufacturing the semiconductor device

Abstract

A semiconductor device has a module structure in which a semiconductor element and a circuit layer are electrically connected to each other by a wire. A front metal layer is formed on a surface of a top side electrode of the semiconductor element and the wire is bonded to the front metal layer by wire bonding. The front metal layer has a higher hardness than the top side electrode or the wire. A bonding interface of the wire with the metal film has a recrystallization temperature that is equal to or higher than 175° C. According to this structure, it is possible to improve the power cycle resistance of the semiconductor device.

What is claimed is: 
     
       1. A semiconductor device that is formed by electrically connecting an electrode of a semiconductor element and a wire using wire bonding, comprising:
 a metal film that has a higher hardness than the wire and is provided on a surface of the electrode, 
 wherein the wire is bonded to the metal film by the wire bonding to provide a bonding interface, the bonding interface of the wire with the metal film has a recrystallization temperature that is higher than 175° C., and the semiconductor element has a bonding temperature that is less than the recrystallization temperature of the bonding interface, and 
 wherein the bonding interface of the wire has a crystal grain size that is only equal to or less than 15 μm, and a portion which is away from the bonding interface of the wire includes a crystal grain with a grain size greater than 15 μm. 
 
     
     
       2. The semiconductor device according to  claim 1 , wherein the metal film is a nickel-plated film. 
     
     
       3. The semiconductor device according to  claim 2 , wherein the nickel-plated film has a thickness ranging from 3 μm to 7 μm. 
     
     
       4. The semiconductor device according to  claim 1 , wherein the metal film is a copper-plated film. 
     
     
       5. The semiconductor device according to  claim 4 , wherein the copper-plated film has a thickness ranging from 4.5 μm to 10.5 μm. 
     
     
       6. The semiconductor device according to  claim 1 , wherein the wire has a higher hardness than that of the electrode. 
     
     
       7. The semiconductor device according to  claim 6 , wherein the metal film is a nickel-plated film. 
     
     
       8. The semiconductor device according to  claim 7 , wherein the nickel-plated film has a thickness ranging from 3 μm to 7 μm. 
     
     
       9. The semiconductor device according to  claim 6 , wherein the metal film is a copper-plated film. 
     
     
       10. The semiconductor device according to  claim 9 , wherein the copper-plated film has a thickness ranging from 4.5 μm to 10.5 μm. 
     
     
       11. A method for manufacturing a semiconductor device according to  claim 1  in which an electrode of a semiconductor element is electrically connected to a wire, comprising:
 providing a metal film having a hardness that is higher than that of the wire on a surface of the electrode; and 
 bonding the wire to the metal film using ultrasonic vibration to provide a bonding interface having a crystal grain size that is only equal to or less than 15 μm. 
 
     
     
       12. The semiconductor device according to  claim 1 , wherein the wire is made of an aluminum alloy including 0.2 to 2.0 mass % of iron and the balance aluminum with a purity of 99.99% or more. 
     
     
       13. The semiconductor device according to  claim 1 , wherein the wire is directly connected to the metal film. 
     
     
       14. A semiconductor device that is formed by electrically connecting an electrode of a semiconductor element and a wire using wire bonding, comprising:
 a metal film that is a copper film consisting of copper, that has a thickness ranging from 4.5 μm to 10.5 μm, that has a higher hardness than that of the wire, and that is provided on a surface of the electrode, 
 wherein the wire has a higher hardness than that of the electrode and is bonded to the metal film by the wire bonding to provide a bonding interface, and the bonding interface of the wire with the metal film has a recrystallization temperature that is higher than 175° C. 
 
     
     
       15. The semiconductor device according to  claim 1 , wherein the bonding interface of the wire has a crystal grain size that is only equal to or less than 15 μm, and a portion which is away from the bonding interface of the wire includes a crystal grain with a grain size greater than 15 μm. 
     
     
       16. The semiconductor device according to  claim 1 , wherein the wire is made of an aluminum alloy including 0.2 to 2.0 mass % of iron and the balance aluminum with a purity of 99.99% or more. 
     
     
       17. The semiconductor device according to  claim 1 , wherein the wire is directly connected to the metal film. 
     
     
       18. A method for manufacturing a semiconductor device according to  claim 15  in which an electrode of a semiconductor element is electrically connected to a wire, comprising:
 providing a metal film having a hardness that is higher than that of the wire on a surface of the electrode; and 
 bonding the wire to the metal film using ultrasonic vibration to provide a bonding interface having a crystal grain size that is only equal to or less than 15 μm.